Is Hypercapnea a Predictor of Better Survival in the Patients who Underwent Mechanical Ventilation for Chronic Obstructive Pulmonary Disease (COPD)?

BACKGROUND: There are contradictory reports concerning hypercapnia as a predictor of a better outcome in COPD. This study examined the clinical implications of hypercapnea in COPD patients (M:F = 59:19) who required mechanical ventilation. METHODS: The clinical parameters at the time of MICU admission, the total ventilation time, the APACHE II score and the pulmonary function testing were retrospectively analyzed between the survivors and nonsurvivors. RESULTS: Univariate analysis showed that compared with the nonsurvivors, the survivors had lower AaDO2 values (59.8±53.5 vs. 105.0±73.3 mmHg, p=0.000), higher PaCO(2) values (64.9±16.0 vs. 48.9±17.8 mmHg, p=0.000), lower APACHE II scores (19.0±3.8 vs. 24.1±5.1, p=0.002), the more frequent application of initial noninvasive positive pressure ventilation (44.0 vs. 14.3%, p=0.008), and a lower combined rate of septic shock (4.0 vs. 39.3%, p=0.000). Multivariate analysis revealed that a lower PaCO(2) (OR: 0.94, p=0.008), the presence of septic shock (OR: 10.16, p=0.011), a higher APACHE II score (OR: 1.22, p=0.040) and a longer ventilation time (OR: 1.002, p=0.041) were the risk factors for mortality. A lower PaCO(2) was also verified as the predictor for mortality by multivariate analysis when excluding septic shock. CONCLUSIONS: Hypercapnia at admission is thought to be an independent predictor of better survival for the COPD patients who require mechanical ventilation.